Preliminary studies on a unique strain of laboratory Beagles have identified a spontaneous inherited glaucoma that may represent the most promising biomedical model discovered to date. To thoroughly document this unique animal model and determine the similarities of the disease to the different types of glaucoma in man, the clinical course of the disease will be closely followed by consecutive detailed ophthalmic pocedures, noting the inter-relationships of changes in the iridocorneal angle, elevated intraocular pressure, buphthalmia and lens and vitreous positions. Further studies are essential to confirm the autosomal recessive heredity. The outflow of aqueous humor at various stages of the disease will be estimated by Schiotz tonography, constant pressure perfusion, pressure decay curves and fluorescein turnover rates. The glaucomatous beagles at different stages of the disease will be evaluated as a model to evaluate efficacy and mechanisms of various pharmacologic agents. Control and glaucomatous beagles will be evaluated for evidence of diurnal variation in intraocular pressure, essential for drug studies. Selected applanation and the Schiotz tonometers will be calibrated in the glaucomatous beagle globes to ascertain validity of drug studies. Selected drugs affecting either predominately inflow, outflow or both areas of aqueous humor dynamics in the early (open angle) and advanced (closed angle) glaucomatous eyes. The glaucomatous beagle will also be evaluated as a model to investigate the effects of elevated intraocular pressure on the ocular tissues at various stages of the disease. The effects on the retina and optic disk will be determined by serial ophthalmoscopy, stereophotography and fluroscein angiography. Axtoplasmic flow in the glaucomatous optic nerve will be measured. The retinal vasculature will be evaluated by trypsin digestion; the choroid and optic nerve vasculature by latex casts and histology. At various phases of the disease, the ocular tissues will be analyzed by light, scanning and transmission microscopy.